There is a need for a display device capable of displaying 3-dimensional images. Such a display device may be used as a new media in an advertising field, a home 3-dimensional multimedia image display terminal, an image display terminal for simulation and education/training, a visualization image display terminal for precise measurement and diagnosis, a medical 3-dimensional image display terminal, a 3-dimensional image monitor for video conference and advertisement, a 3-dimensional television for broadcasting, an image display terminal for education/entertainment, manufacturing parts for various kinds of special environments, an image device for 3-dimensional game, various heads-up displays for airplanes and vehicles, or the like.
Methods of displaying 3-dimensional images may be classified into two types: a 2-viewpoint type, and a multiple viewpoint type. The 2-viewpoint type displays respective images for left and right eyes one by one, whereas the multiple viewpoint type displays a binocular parallax image in wide variety of directions. In case of the multiple viewpoint type, a resolution decreases in proportion to the number of viewpoints, whereas a degree of freedom of viewing position is higher, so that it is possible to naturally see the 3-dimensional image.
As a method of focusing the image data for left and right eyes on the left and right eyes, respectively, a parallax barrier method, a lenticular method or the like are used.
FIG. 1 is an exploded perspective view of a related art display device capable of displaying 2-dimensional and 3-dimensional images, and FIG. 2 is a schematic view illustrating display of the 3-dimensional image using the related art display device of FIG. 1.
A liquid crystal display (LCD) device for displaying a 3-dimensional image using a parallax barrier panel 3 is provided with a backlight unit 1, an image display panel 5 for displaying an image by light generated from the backlight unit 1. The parallax barrier panel 3 is disposed between the backlight unit 3 and the image display panel 5.
The image display panel 5 is has an upper substrate on which a color filter layer is formed, and a lower substrate on which a thin film transistor (TFT) as a switching device and a pixel electrode are formed. A liquid crystal layer is interposed between the upper and lower substrates.
The parallax barrier panel 3 utilizes the principle of binocular parallax between left and right eyes, which makes it possible to see the image 3-dimensionally. As shown in FIG. 2, image data for the left eye and image data for the right eye are inputted into the image display panel 5 (minimally, two viewpoints). It is possible to see the 2-dimensional image as a 3-dimensional image by intentionally focusing left and right eye images on an observer's left and right eyes, respectively.
That is, by inputting two image data on sets a screen and producing left and right eye images separately focused on the left and right eyes, respectively, the 2-dimensional plane image can be perceived as a 3-dimensional image.
The parallax barrier panel 3 is divided into a plurality of areas 4a for propagating the light toward an observer's left eye, and a plurality of areas 4b for propagating the light toward an observer's right eye.
Assuming that a distance between the left and right eyes is about 65 mm and a distance within which the observer can see the image ranges from 25 cm to 30 cm, for example, the parallax barrier panel 3 should be designed such that the left and right images are focused on the left and right eyes, respectively, within distances the in range of 25 cm to 30 cm from the image display panel 5.
However, the parallax barrier panel 3, which is used as a switch panel, generally uses a twisted nematic (TN) mode liquid crystal panel in which a common electrode is disposed on an upper substrate and a pixel electrode is disposed on a lower substrate. The viewing angle is quite narrow and a color change becomes large over a range of viewing angles of the 3-dimensional image (see FIG. 9A).
The response speed of a liquid crystal is slow in response to an electric field in the TN mode switching panel, and this also limits the quality of the display.